[PowerPC] Try to fold sqrt/sdiv test results with the branch.

Summary: The patch tries to fold sqrt/sdiv test node, i.g FTSQRT, XVTDIVDP, and the branch, i.e br_cc if they meet these patterns:
(br_cc seteq, (truncateToi1 SWTestOp), 0) -> (BCC PRED_NU, SWTestOp)
(br_cc seteq, (and SWTestOp, 2), 0) -> (BCC PRED_NE, SWTestOp)
(br_cc seteq, (and SWTestOp, 4), 0) -> (BCC PRED_LE, SWTestOp)
(br_cc seteq, (and SWTestOp, 8), 0) -> (BCC PRED_GE, SWTestOp)
(br_cc setne, (truncateToi1 SWTestOp), 0) -> (BCC PRED_UN, SWTestOp)
(br_cc setne, (and SWTestOp, 2), 0) -> (BCC PRED_EQ, SWTestOp)
(br_cc setne, (and SWTestOp, 4), 0) -> (BCC PRED_GT, SWTestOp)
(br_cc setne, (and SWTestOp, 8), 0) -> (BCC PRED_LT, SWTestOp)

Reviewed By: steven.zhang

Differential Revision: https://reviews.llvm.org/D94054